The city of Tomioka (xª) in southwestern Gunma Prefecture is the site of Japan's first modern silk factory, established in 1872. The Tomioka Silk Mill served as a model for other silk mills in the country in an effort to modernize Japan's silk industry during the Meiji Period, when far reaching reforms were carried out in all aspects of society in order to catch up with the West. The mill played an important role in making the textile industry Japan's most important industry for several decades, sustaining the growth of Japan's economy.
Not only is the Tomioka Silk Mill Japan's oldest modern silk reeling factory, it was also one of the world's largest silk mills at the time of its construction. Thanks to the improvements introduced by the mill, raw silk became a major commodity that was exported from Japan across the world, and silk produced in Tomioka enjoyed a good reputation overseas for its high quality. The original buildings of the mill are well preserved and are the central piece out of four silk related sites in Gunma Prefecture that were enlisted as World Heritage Site in 2014.
The other three sites are found in nearby cities: the Tajima Yahei Sericulture Farm excelled in the research of silkworm egg production, the Arafune Cold Storage enabled multiple harvests per year with its naturally cooled environment for storing silkworm eggs, and the Takayama-sha Sericulture School introduced major improvements in the process of rearing silkworms into cocoons, which would then be processed at the Tomioka mill.